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51 Cards in this Set
- Front
- Back
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What is the nervous system? |
•mastercontrolling and communicating system of the body • hasthree overlapping functions |
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Name the three overlapping functions of the nervous system? |
1. Sensoryinput 2. Integration 3. Motoroutput |
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Explain Sensory input |
Uses sensory receptors to monitorchanges inside and outsidethe body. (Driving you see a redlight) |
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Explain Integration |
Processes and interprets sensory inputand decides what should be done. (Red means stop) |
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Explain motor output |
produces a response by activating effectormuscles. (Foot goes for the brake) |
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What are the two parts of the nervous system? |
Central Nervous system Peripheral Nervous system |
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Describe the central nervous system? |
•brainand spinal cord •integrating and command center of NS •interprets sensory input and dictates motor responses based on past experience, reflexes and currentconditions |
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Describe the peripheral nervous system? |
•nervesextending from brain and spinal cord • thepart of the NS outside the CNS |
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What are two divisions of the PNS? |
Sensory (afferent) division Motor (efferent) division |
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Explain the sensory afferent division? |
•sensory receptor impulses to CNS •somatic afferent - from skin, skeletal muscle and joints •visceral afferent - from visceral organs such as the heart |
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Explain the motor efferent division? |
•impulsesfrom CNS to effector organs i.e. muscles and glands •voluntary NS - from CNS to skeletalmuscles •involuntary NS - from CNS to smooth and cardiac muscle and glands. •Sympathetic stimulates and parasympathetic inhibits |
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How many types of glial cells do we have and where are they located? |
• 6different types of glial cells • 4 inthe CNS 2 in the PNS |
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Name the glial cells found in the CNS? |
Astrocyte Microglial cell Ependymal cell Oligodendrocyte |
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Name the glial cells found in the PNS? |
Schwann cells Satellite cells |
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What are neurons? |
•nucleus and most organelle found in the cell body • atypical neuron has numerous highly branched extensions called dendrites whichreceive impulses |
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Explain axons? |
• aneuron also has a single long extension called an axon which generates andtransmits impulses to other cells •signals that travel along the axon are generated at the axon hillock |
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Explain the branches of an axon? |
•axonend divides into branches called synaptic termini which transmit information toanother cell at a junction called a synapse |
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What are neurotransmitters? |
Chemicalmessengers that pass information between the cells at thesynapse |
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What is a presynaptic cell? |
thetransmitting neuron |
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What is a a postsynaptic cell? |
The receiving neuron |
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What is the function of glial cells that neurons associate with? |
which provide a supportive scaffolding for neurons |
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What is the correct processing path takenwhen you see a football and go to kick it? |
Sensoryneuron – interneuron - motor neuron |
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What are the two classifications of neurons? |
Structural and functional classification. |
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What is the structural classification of neurons? |
it is basedon the number of processes extending from cell body -Multipolar -Bipolar -Unpolar |
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What are reflexes? |
•rapidautomatic responses to stimuli in which a particular stimulus always causes thesame response •spinal cord acts independently of the brain •occur over reflex arcs that have five essential components |
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Explain environment in the exterior and the interior of a cell? |
• ionsare unequally distributed between the interior of a cell and the surroundingfluid •interior of cell is negatively charged in relation to surrounding fluid •separated electrical charges of opposite sign have potential energy |
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What is Membrane potential? |
theattraction of opposite charges across the plasma membrane |
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What is Resting potential? |
•potentialof a neuron that is not sending a signal. • -60to -80 mV, minus indicating cytoplasmic sideof membrane. |
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Explain resting potential? |
•ionpumps and channels establish the resting potential of a neuron • ionsare unequally distributed between the interior and exterior of the cell given anegative charge inside and a positive outside the cell • theattraction between oppositely charged ions across the membrane is a source ofpotential energy or voltage, -60 to -80mV (- indicating cytoplasmic sideof membrane) is the resting potential. |
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What happens during resting membrane potential? |
The Na+-K+ pump pumps sodium out of the cell. |
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What generates an impulse? |
•membranepotential changes in response to a signal due to gated ion channels that openor close •gated ion channels alter the membranes permeability to particular ions andtherefore membrane potential |
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What is Hyperpolarisation(increase in negativity)? |
results fromthe outflow of + (K+)ions or inflow of – ions |
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What is Depolarisation (decrease innegativity)? |
•results from a reduction of membrane potential (moves closer to zero) •inflow of + ions (Na+) |
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Name two types of nerve signals |
Graded potential Action potential (nerve impulse) |
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Explain graded potential |
•shiftin membrane potential•magnitude varies with strength of stimulus •signals that do not flow along axon • rolein generation of nerve signals |
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Explain Action potential |
•resultsdue to massive change in membrane voltage when threshold of -55 mV is reached •arises due to voltage-gated ion channels which open or close depending on theparticular level |
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What happens in action potential? |
•mostly Na+ channels open resulting in inflowof Na+ •increased depolarisationresults in opening of more channels (positive feedback) • onceinitiated, the magnitude is independent of strength of stimulus |
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What is Depolarisation? |
A stimulus causes Na+ channels to openand Na+ rushes into the cell. When the threshold level is reached more channelsopen due to positive feedback. |
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What is Repolarization? |
Rising phase lasts for 1ms only. There isan increase in K+ (activation gates open) permeability and a decrease in Na+permeability (inactivation gates close) |
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What is Restingstate? |
Voltage-gated channels are closed. Na+has a closed activation and open inactivation gate. Both must be open for Na+to pass). K+ has an activation gate only that is closed. |
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What is Hyperpolarisation? |
K+ permeability lasts longer than needed(channels remain open). The Na+ channels begin to reset. Sodium-potassium pump restores ionconditions |
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Explain the conduction of action potentials |
•anaction potential is generated as Na+ ionsflow in at one location along an axon • the depolarisationspreads to the neighboring region of the membrane, initiating an actionpotential there • theoriginal region repolarises as K+ ions flow out • the depolarisation-repolarisationprocess is repeated as the action potential is propagated down the axon to thesynaptic terminals |
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Name 2 synapses? |
Electrical synapses Chemical synapses |
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What are electrical synapses? |
•contain gap junctions which allow electrical current to flow • lesscommon |
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What are chemical synapses? |
•involve the release of a chemical neurotransmitter by the presynaptic neuron |
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Describe chemical synapse? |
1.Actionpotential arrivesdepolarising thepresynapticmembrane. Depolarisationopens voltage gated channelsWhich trigger an inflow of Ca2+ 2. Increase Ca2+ levels causes synaptic vesicles tofuse with presynapticmembrane, releasing neurotransmitter into the synaptic cleft 3. The neurotransmitters diffuse acrossthe cleft and bind to ligand-gated ion channels in postsynapticmembrane 4. Binding opens the channel and allowsspecific ions to cross resulting in graded potentials (permeable to Na+ causes a depolarisation) |
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Assume that an excitatory postsynapticpotential (to generate axon at axon hillock) is being generated on thedendritic membrane. What must occur toachieve the action potential? |
Sodiumions flowing into the cell. |
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What are the twofactors affecting action potential conduction velocity? |
•axondiameter •degreeof myelination |
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How does axon diameter affect the conduction velocity? |
•thelarger the axon diameter the faster it conducts impulses •larger axons offer less resistance to the flow of local currents |
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How do unmyelinatedaxons affect the conduction velocity? |
•actionpotentials are generated at sites immediately adjacent to each other andconduction is relatively slow. •termed continuous conduction |
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How do myelinatedaxons affect the conduction velocity? |
•dramaticallyincrease the rate of action potential propagation by acting as an insulator •termed saltatoryconduction •current passes only at the nodes of ranvierwhere the axon is bare and Na+channels are concentrated |
